not applicable
not applicable
1. Field of Invention
A workpiece cut with a circular saw blade has material removed by the cutting teeth upstream of the blade center. This xe2x80x9ckerfxe2x80x9d needs to be kept laterally aligned with the plane of the blade so that saw teeth moving upward through the kerf downstream of the blade do not contact the cut sides of the workpiece. A board ripped having internal stresses may spring together, binding the rear of the sawblade. These teeth then cut further into the cut edges, causing kickback and ragged cuts.
2. Discussion of Prior Art
Splitters have been part of tablesaws for nearly 100 years. Most combine splitter and guard. This creates problems when narrow pieces are ripped, because the guard interferes with controling the workpiece. Over 90% of guards (with splitters attached) are removed from tablesaws because of this problem, leaving the saw without either splittter or guard. A typical splitter aassembly for a table saw is shown in U.S. Pat. No. 4,625,604. Downstream of the blade is a splitter device which maintains separation of the cut material by virtue of its location in the kerf. Other types of splitter devices are shown, for example, in U.S. Pat. No. 2,530,867. The device is of a fixed thickness and, hence, cannot readily accommodate varying thickness in saw blades, particularly in respect of the newer ultrathin saw blades. U.S. Pat. No. 3,566,934 shows an lateraly adjustable splitter device with opposing longitudinally offset resilient contacts which fit within the kerf defined by the saw blade cut. This device recognizes the need for lateral adjustment, but is complicated, expensive, and is not applicable for retrofit on existing tablesaws
It is common for woodworkers to insert a thin flat stick into a throatplate behind the blade to act as a splitter. These are not laterally adjustable. Previously I have taught inserting a drill bit into a throatplate behind a sawblade.
Unless lateral splitter adjustment is accurate, splitters must be thinner than the kerf to compensate for alignment errors. These thin splitters cannot keep the kerf fully open. Because of this conventional splitters rely on pawls on top of the workpiece to stop kickback after it starts. Ragged cuts and xe2x80x9ckickbackxe2x80x9d can result from xe2x80x9csplittersxe2x80x9d which are narrower than the kerf, or are misaligned with the kerf, or are not stable laterally.
No existing splitter is both infinitly adjustable for lateral position and easily adjusted for blade width.
Splitter-guard combination devices cannot be used for non through cuts, such as dado and resaw cuts.
This invention provides infinite lateral adjustment and variable splitter width. It is very simple and inexpensive to manufacture. Retrofit installation is as simple as replacing a throatplate in one variation. A splitter equal in dimension to the kerf prevents binding on the rear of the circular blade. Changing sawblade kerf width requires changing size and therefore splitter lateral postiton for best anti-kickback effect. The splitter width in this device can be changed without tools in seconds. Changing lateral position requires 5 seconds and a dime or a screwdriver. Accurate lateral adjustment, precise splitter sizing, and solid fixation of a splitter keeps the rear teeth of a circular blade from touching the wood inside the kerf. This aligns the board during the cut and keeps the kerf fully open, which combined with holding the workpiece down, prevents the major causes of kickback.
One aspect of this invention shows a cylindrical splitter pin, rotated around an axis to move laterally while rotated. This laterally adjustable splitter pin can have the right kerf dimension by easily changing splitters, splitter pins, or spacer bushings.
A further aspect of this invention combines two offset splitter pins with bearing bushings to eliminate friction from boards which try to pinch the blade, but cannot because the splitter bearings prevent pinching.
Conventional splitters with guard attached must be removed for rip cuts where the blade is close to the fence. This splitter does not need to be removed for any cut and can be used with hold down springs and overhead guards.
Another aspect of this invention is to provide a simple, economical, adjustable splitter for handheld power circular saws which also makes straight line cuts easier to accomplish.
One objective is to provide a tablesaw throatplate which has an integral laterally adjustable, variable width splitter. Another object of this invention is to provide a splitter which can be easily attached to an existing sawdeck or tablesaw throatplate.
Another object is to provide a tablesaw splitter which does not interfere with hold downs and guards positioned above the sawblade.
Another object is to provide a splitter for hand held power saws which keeps the rear of the blade from moving lateraly into the workpiece.
A further objective is to provide a very economical splitter to replace those removed when the combination splitter/guard is temporarily or permanently removed.
According to an aspect of the invention, there is provided a device for removably securing a laterally adjustable circular saw splitter device downstream of a saw blade, the device comprising a splitter dowel holder able to rotate about an axis parallel to a sawblade, and a variable size splitter dowels protruding through the saw deck from the splitter dowel holder. Certain variations of the invention are very simple and inexpensive to produce, while others allow greater flexibility in operation.